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[Safe code] Clean up Guid.TryFormatX #110923

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merged 4 commits into from
Dec 27, 2024
+61 −75
Merged

[Safe code] Clean up Guid.TryFormatX #110923

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70086cf
Guid cleanup: hex format
EgorBo Dec 23, 2024
cf36bce
Optimize TryFormatX
EgorBo Dec 24, 2024
94cd16a
revert unrelated changes
EgorBo Dec 24, 2024
61f5fe7
Refactor switch statement in Guid parsing
EgorBo Dec 26, 2024
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136 changes: 61 additions & 75 deletions src/libraries/System.Private.CoreLib/src/System/Guid.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -423,29 +423,15 @@ public static bool TryParseExact(ReadOnlySpan<char> input, [StringSyntax(StringS
input = input.Trim();

var parseResult = new GuidResult(GuidParseThrowStyle.None);
bool success = false;
switch ((char)(format[0] | 0x20))
{
case 'd':
success = TryParseExactD(input, ref parseResult);
break;

case 'n':
success = TryParseExactN(input, ref parseResult);
break;

case 'b':
success = TryParseExactB(input, ref parseResult);
break;

case 'p':
success = TryParseExactP(input, ref parseResult);
break;

case 'x':
success = TryParseExactX(input, ref parseResult);
break;
}
bool success = (char)(format[0] | 0x20) switch
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Is the cast to char actually necessary here? It should work without it and that would make smaller IL and avoid an extra zero extension that the JIT has to otherwise remove here

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@tannergooding hm. I've removed the cast but the codegen hasn't changed. But I guess it is still makes sense to remove it as useless

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I'd guess the JIT is recognizing it as unnecessary and removing it already; just something small that caught my eye as likely unneeded

{
'd' => TryParseExactD(input, ref parseResult),
'n' => TryParseExactN(input, ref parseResult),
'b' => TryParseExactB(input, ref parseResult),
'p' => TryParseExactP(input, ref parseResult),
'x' => TryParseExactX(input, ref parseResult),
_ => false
};

if (success)
{
Expand Down Expand Up @@ -1108,24 +1094,6 @@ private static unsafe int HexsToChars<TChar>(TChar* guidChars, int a, int b) whe
return 4;
}

private static unsafe int HexsToCharsHexOutput<TChar>(TChar* guidChars, int a, int b) where TChar : unmanaged, IUtfChar<TChar>
{
guidChars[0] = TChar.CastFrom('0');
guidChars[1] = TChar.CastFrom('x');

guidChars[2] = TChar.CastFrom(HexConverter.ToCharLower(a >> 4));
guidChars[3] = TChar.CastFrom(HexConverter.ToCharLower(a));

guidChars[4] = TChar.CastFrom(',');
guidChars[5] = TChar.CastFrom('0');
guidChars[6] = TChar.CastFrom('x');

guidChars[7] = TChar.CastFrom(HexConverter.ToCharLower(b >> 4));
guidChars[8] = TChar.CastFrom(HexConverter.ToCharLower(b));

return 9;
}

// Returns the guid in "registry" format.
public override string ToString() => ToString("d", null);

Expand Down Expand Up @@ -1379,49 +1347,67 @@ internal unsafe bool TryFormatCore<TChar>(Span<TChar> destination, out int chars
return true;
}

private unsafe bool TryFormatX<TChar>(Span<TChar> destination, out int charsWritten) where TChar : unmanaged, IUtfChar<TChar>
private bool TryFormatX<TChar>(Span<TChar> dest, out int charsWritten) where TChar : unmanaged, IUtfChar<TChar>
{
if (destination.Length < 68)
if (dest.Length < 68)
{
charsWritten = 0;
return false;
}

// {0xdddddddd,0xdddd,0xdddd,{0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd}}
dest[0] = TChar.CastFrom('{');
dest[1] = TChar.CastFrom('0');
dest[2] = TChar.CastFrom('x');
dest[3] = TChar.CastFrom(HexConverter.ToCharLower(_a >> 28));
dest[4] = TChar.CastFrom(HexConverter.ToCharLower(_a >> 24));
dest[5] = TChar.CastFrom(HexConverter.ToCharLower(_a >> 20));
dest[6] = TChar.CastFrom(HexConverter.ToCharLower(_a >> 16));
dest[7] = TChar.CastFrom(HexConverter.ToCharLower(_a >> 12));
dest[8] = TChar.CastFrom(HexConverter.ToCharLower(_a >> 8));
dest[9] = TChar.CastFrom(HexConverter.ToCharLower(_a >> 4));
dest[10] = TChar.CastFrom(HexConverter.ToCharLower(_a));
dest[11] = TChar.CastFrom(',');
dest[12] = TChar.CastFrom('0');
dest[13] = TChar.CastFrom('x');
dest[14] = TChar.CastFrom(HexConverter.ToCharLower(_b >> 12));
dest[15] = TChar.CastFrom(HexConverter.ToCharLower(_b >> 8));
dest[16] = TChar.CastFrom(HexConverter.ToCharLower(_b >> 4));
dest[17] = TChar.CastFrom(HexConverter.ToCharLower(_b));
dest[18] = TChar.CastFrom(',');
dest[19] = TChar.CastFrom('0');
dest[20] = TChar.CastFrom('x');
dest[21] = TChar.CastFrom(HexConverter.ToCharLower(_c >> 12));
dest[22] = TChar.CastFrom(HexConverter.ToCharLower(_c >> 8));
dest[23] = TChar.CastFrom(HexConverter.ToCharLower(_c >> 4));
dest[24] = TChar.CastFrom(HexConverter.ToCharLower(_c));
dest[25] = TChar.CastFrom(',');
dest[26] = TChar.CastFrom('{');
WriteHex(dest, 27, _d);
WriteHex(dest, 32, _e);
WriteHex(dest, 37, _f);
WriteHex(dest, 42, _g);
WriteHex(dest, 47, _h);
WriteHex(dest, 52, _i);
WriteHex(dest, 57, _j);
WriteHex(dest, 62, _k, appendComma: false);
dest[66] = TChar.CastFrom('}');
dest[67] = TChar.CastFrom('}');
charsWritten = 68;
return true;

fixed (TChar* guidChars = &MemoryMarshal.GetReference(destination))
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static void WriteHex(Span<TChar> dest, int offset, int val, bool appendComma = true)
{
TChar* p = guidChars;

// {0xdddddddd,0xdddd,0xdddd,{0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd}}
*p++ = TChar.CastFrom('{');
*p++ = TChar.CastFrom('0');
*p++ = TChar.CastFrom('x');
p += HexsToChars(p, _a >> 24, _a >> 16);
p += HexsToChars(p, _a >> 8, _a);
*p++ = TChar.CastFrom(',');
*p++ = TChar.CastFrom('0');
*p++ = TChar.CastFrom('x');
p += HexsToChars(p, _b >> 8, _b);
*p++ = TChar.CastFrom(',');
*p++ = TChar.CastFrom('0');
*p++ = TChar.CastFrom('x');
p += HexsToChars(p, _c >> 8, _c);
*p++ = TChar.CastFrom(',');
*p++ = TChar.CastFrom('{');
p += HexsToCharsHexOutput(p, _d, _e);
*p++ = TChar.CastFrom(',');
p += HexsToCharsHexOutput(p, _f, _g);
*p++ = TChar.CastFrom(',');
p += HexsToCharsHexOutput(p, _h, _i);
*p++ = TChar.CastFrom(',');
p += HexsToCharsHexOutput(p, _j, _k);
*p++ = TChar.CastFrom('}');
*p = TChar.CastFrom('}');

Debug.Assert(p == guidChars + charsWritten - 1);
dest[offset + 0] = TChar.CastFrom('0');
dest[offset + 1] = TChar.CastFrom('x');
dest[offset + 2] = TChar.CastFrom(HexConverter.ToCharLower(val >> 4));
dest[offset + 3] = TChar.CastFrom(HexConverter.ToCharLower(val));
if (appendComma)
{
dest[offset + 4] = TChar.CastFrom(',');
}
}

return true;
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
Expand Down